Uniform System for the Evaluation of Substances. IV. Distribution and intake

This is the fourth article in the series on USES, the Uniform System for the Evaluation of Substances. This article describes the modelling approach used to predict concentrations in the environmental media (air, surface water, agricultural soil and groundwater) and the intake media for humans (fish, drinking water, root crops, leaf crops, meat and milk) and for predatory birds and mammals (fish and earthworms). Distribution and intake are estimated on two spatial scales: locally near a point source, and regionally over a larger area. This article focuses on the local distribution and the general intake models. Local distribution is modelled in a hypothetical standard environment, using typical environmental characteristics. Humans and predators are assumed to be exposed to food products from the contaminated system. The choice of models in a system like USES, is limited by the small data sets legally required for risk assessment purposes. Therefore, USES focuses on relatively simple models, and is able to work with the limited input data.